The present invention relates in general to equipment and techniques for monitoring the conditions in a nuclear reactor, and in particular to a new and useful method for measuring reactivity in a reactor which is automatically normalized during range changes.
It is known that neutron population is related to reactivity and kinetic equations have been developed to measure neutron populations.
The use of an integral form for reactor kinetic equations to compute reactivity from neutron population information has been described in various publications on nuclear reactor kinetics, for example "Physics of Nuclear Kinetics" by G. R. Keepin, Addison-Wesley, 1965.
A portable digital system for rapid on-line calculations of reactivity during nuclear plant physics testing is disclosed in "Development of Digital Reactivity Meter Status Report" by W. G. Pettus and S. B. Revkin, BAW-TM-464, Jun, 12, 1969. Also see "A Fast Digital Reactivity Calculation and Logging System" by J. M. Lovall and H. J. Worsham, IEEE, NS-19(1) pp. 837-839, February 1972.
Babcock & Wilcox (a McDermott Company) has constructed, used and sold a system using a small digital computer for on-line determinations of reactivity. In this system, renormalization factors between ranges were determined from measurements on a linear amplifier. These factors were then introduced into the digital program of the computer, to be used whenever a range change occurred. This required the storage of numbers corresponding to a calibration of the amplifier and measured range ratios. The use of such pre-stored numbers introduced inaccuracy into the normalization factors, caused by improper calibration or drift in the amplifier system during use. This resulted in "jumps" in the indicated reactivity during actual tests conducted on nuclear reactors.